A majority of vehicles include turn signals which provide a visual signal to nearby motorists and pedestrians of an anticipated change in the direction of travel of the vehicle. Typically, the turn signals include a pair of lights mounted on both the front and rear of the vehicle. In particular, left and right turn signals are generally mounted on both the front and rear of the vehicle.
The turn signals are generally activated by the driver of the vehicle by means of a turn signal selector such that the turn signals flash corresponding to the direction of the anticipated turn. Typically, the turn signal selector is a lever arm on the steering column which generally has three positions, namely, a left turn position, a right turn position and a neutral position. By placing the lever in the left turn position, the left turn signals on both the front and the rear of the vehicle are activated and will flash accordingly. Likewise, if the turn signal selector is placed in the right turn position, the right turn signals on both the front and rear of the vehicle are activated and will flash. In contrast, if the lever is placed in the neutral position, neither the right nor the left turn signals will be activated.
In order to provide the driver with an indication that the turn signals have been activated, many vehicles include a visual turn signal indicator. The visual turn signal indicator generally includes left and right visual displays which provide first and second predetermined visual signals, respectively, in response to movement of the turn signal selector to the left turn position and the right turn position, respectively. Typically, the left visual display is a left facing arrow which blinks during the time period which the left turn signals are activated. In a like fashion, the right visual display is generally a right facing arrow which blinks during the time period in which the right turn signals are activated.
In addition to visual turn signal indicators, a number of vehicles also include audible turn signal indicators. Conventional audible turn signal indicators generally include a sound generator and one or more speakers. Thus, upon actuation of either the left turn signal or the right turn signal, the sound generator of a conventional audible turn signal indicator drives the speakers to emit a predetermined sound. Typically, the predetermined sound is a series of rhythmic clicks which provide an audible indication to the driver that either the left turn signal or the right turn signal is activated. In addition, the predetermined sound emitted by conventional audible turn signal indicators is the same regardless of whether the left turn signal or the right turn signal has been activated.
Audible turn signal indicator systems have also been developed which notify the driver if the turn signals have not been extinguished or cancelled within a predetermined time period. Thus, the driver will be notified if the turn signal has not been cancelled shortly after completion of a turn or a lane change. For example, audible turn signal indicator systems have been developed with emit a tone, buzzer, bell or voice synthesized message which warns the driver if a turn signal has not been cancelled within a predetermined time period. See, for example, U.S. Pat. No. 5,309,143 which issued May 3, 1994 to Brown, et al. and is assigned to Donald Adkins; U.S. Pat. No. 5,218,340 which issued Jun. 8, 1993 to Shannon, Jr., et al.; U.S. Pat. No. 4,924,208 which issued May 8, 1990 to Coughlan; and U.S. Pat. No. 3,806,868 which issued Apr. 23, 1974 to Portman.
In addition, U.S. Pat. No. 5,099,222 which issued Mar. 24, 1992 to Campagna and is assigned to Fact Games, Ltd. discloses an audible turn signal indicator which produces an audible signal which progressively increases in volume as the turn signals remain activated for longer periods of time. Further, U.S. Pat. No. 2,258,747 which issued Oct. 14, 1941 to Doane discloses an audible turn signal indicator which provides a tactile signal to warn the vehicle's driver that the turn signal is activated. For example, the tactile signal can include a slight vibration of the steering column. Each of these audible turn signal indicators, however, provide the same signal regardless of whether the left turn signals or the right turn signals are activated.